Being a volunteer makes me happy, the feeling is very amazing, I really experienced that. today, I gave a presentation to the students about heart general knowledge as a volunteer, I prepared the slides for a whole week , because the audience  were middle school students, I not only want to make them well understand the content, but aslo want to attract those students with vivid presentation, how to achieve this? I really spent a lot time on the content and the slide, and rehearsaled for many times. today, I thought I was sucessful, because I saw the desired eyes, desiring for knowledge, I felt the atmosphere  of enthusiastic discussion, and I found many hands rasing to want to answer the questions. at that time, the mood was great, I have never having that feelings, maybe I acquired the happiness of helping others by conveying them knowledge.